Automatic telephone-exchange system.



C. L. GOODRUM. AUTOMATIC TELEPHONE EXCHANGE SYSTEM. APPLICATION men JULY 23. 191:

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CHARLES L. GOODRUIVI, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Jan. 29, 191%.

Application filed July 23, 1915. Serial No. 41,587.

To all whom it may concern:

Be it known that 1, GnAnLEs L. GoonRUM, a citizen ofthe United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Automatic 'llelephone-Exchange Systems, of which the following is a full, clear, concise, andexact description.

This invention relates to an automatic telephone system, and was designed to provide circuits for a switch ofthe character of those shown in Patents 1,078,685 and 1,104,451, in which but two wires, that is the talking conductors, are multipled through the various switches used in establishin a telephone connection including the line switch.

In the line switch disclosed in the above mentioned patents, there is a plunger or contact operating device which is individual to each of the lines of a group, and a master switch device is provided whereby the plungers of non-calling lines are normally maintained in a position such that upon their operation they will connect a calling line to an idle trunk.

The mechanism diagrann'llatically indicated within the dotted rectangle in the drawing indicates mechanism which is individual to the subscribers line. As the structure and operation of the switch above re ferred to are clearly described in said patents, it is thought the invention will be readily understoodfrom a description of the operation of the present circuit in establishing a connection.

Assuming that the subscriber, whose substation apparatus is indicated at the left in l the drawing, removes his receiver from the hook, a circuit will be completed from battery through the left winding of line relay 1, left ari'nature and contact of cut-01f relay 2, over the line and through the substation apparatus, back over the lower side of the line, through the armature and back con.

tact of cut-off relay 2, and through the right winding of relay 1, back to battery. Relay 1 pulls up and completes a circuit through the right winding of the plunger operating magnet 3. This magnet is energized and causes the operation of the plunger or contact operating device 4:, by means of which the line spring terminals are forced into engagement with the trunk terminals adjacent thereto.

In accordance with the well-known operation of a switch of this character, it will be understood that the plunger at the time of its operation was associated with a contact set in which an idle trunk terminated. Upon the closure of the line and trunk contacts, a circuit is completed from battery through the left winding of the plunger operating magnet 3, cut-off relay 2 the lower line switch springs, relay 5 and back contact and armature of release magnet 6 to ground. Magnet 3 is maintained energized and relays 2 and 5 attract their armatures. Relay 5 at its inner armature grounds the trunk contact at the master switch, thus causing the idle plungers to move to a position before the neXt idle trunk in a manner clearly explained in the above i'nentioned patents.

Simultaneously with the above, a circuit is completed from battery through stepping relay 7, side switch wiper 17, upper contacts of the line switch, front contact and left armature of relay 2, over the subscribers line and through the substation circuits, and back over the other side of the line, right armature and front contact of relay 2, lower switch springs and relayo to ground, thus interrupting the circuit for the release i'nagnet 6 which would otherwise be established. The energization of relay 7 completes a circuit from battery-through slow-release relay 8 to ground, through back contact and armature of test relay 9.

The subscriber now works his sending device to interrupt the circuit of relay 7. lVith the first deenergization of relay 7 the rotary stepping magnet 10 and the slow-release relay 11 are energized in parallel by a circuit from battery through said relay and magnet in parallel, front contact of relay 8, back contact of relay 7 and back contact of ie lay 9. Relays 8 and 11 being slow to release, remain energized throughout the series of impulses. Each interruption of the line circuit and consequent deenergization of tact and armature of relay 7, and back con-' tact and armature of test relay 9 to ground. The terminals of busy trunks traversed by the lower switch brush will be provided 'with raised potential so the test relay 9 will not be energized. Vhen, however, the switch brush engages the terminal of an idle trunk, which will be connected to earth, relay 9 will pull up, interrupting the circuit for the stepping magnet 13 and completing a circuit from battery through escape magnet 12, front contact and right armature of slow-release relay 8, and front contact and armature of relay 9 to ground. The escape magnet is energized and moves the side switch Wipers to position 3 in a manner which is clearly disclosed in the patent of Charles L. Goodrum 1,281,013,

'June 26, 1917.

Before. the side switch moves to position 3, stepping relay 7 is only momentarily deenergized and, therefore, relay 8 remains energized. This maintains open the circuit from battery through release magnet 6, offnormal contact 15 and side switch wiper 16, which would otherwise be completed through the back contact and armature of relay 8, back contact and armature of relay 7, back contact and armature of relay 9. If the calling subscriber should interrupt his substation circuit while the series of impulses were being sent, stepping relay 7 would fall off, causing the denergization of relay '8 and the completion of the release circuit just described.

At the time the side switch moves out of position 2 and the stepping relay 7 becomes deenergized, relay 9 is energized, but when the side switch reaches position 3 relay 9 becomes deenergized, due to certain changes at the succeeding selector switch, thus opening up the release circuit which would otherwise be established from battery through magnet 6, contact 15, wiper 16, back contact of relay 8 and front contact of relay 9. At the termination of the conversation, relay 9 becomes energized due to circuit changes at the succeeding switch in a man ner which will be well understood from the above mentioned application, Serial No. 35,826.

Should the subscriber, after the operation of his line switch, replace his receiver on the hook without operating his sending device, the stepping relay 7 will become deenergized and a circuit will be completed from battery through the release magnet, the left armature and contact of relay 5, and wiper 16 to ground, through the back contacts and armatures of relays 8, 7 and 9 as before.

The operation of magnet 6 interrupts the circuit of relays 5 and 2 and magnet 3, and if the switch has moved from normal, magnet 6 establishes holding circuit for itself which is maintained through the Dil -1101* mal contact 15, until the switch reaches normal position.

The deenergization of magnet 3 allows the plunger 4E to be retracted. The armatures of relay 2 falling off, connect the subscribers line to his line relay 1, and the retraction of the armatures of relay 5 removes the busy potential from the trunk contact at the master controller, thus permitting the trunk to again be selected.

By the above described invention, means are provided for operating the switch disclosed in the above mentioned patents by means of circuits employing multiples for but two wires, which, as before stated, are the talking conductors, thus considerably simplifying the switch structure and operating circuits therefor without in any manner detracting from their operativeness or practicability.

l Vhat is claimed is:

1. In a telephone exchange system, a telephone line, a switch, terminals of said line at said switch, a trunk line having terminals arranged for engagement by said line tern'iinals, a magnet for causing such engagement, a circuit for said magnet completed upon the initiation of a call upon said line. and a holding circuit for said magnet ex tending through a talking conductor contact of said line and trunk at said switch.

2. In a telephone system, a subscribefis line, a switch, multiple terminals of said line at said switch, trunk lines having terminals arranged to be engaged by said line terminals, a magnet for causing engagement of said line terminals with said trunk terminals, a line relay, a circuit for said mag not controlled by said line relay, and a holding circuit for said magnet extending through talking contacts of said switch.

3. In a telephone exchange system, a telephone line, a switch, multiple terminals of said line at said. switch, trunk lines having ltltl ll I) terminals arranged for engagement by said line terminals, an operating magnet for" causing such engagement, a circuit for said magnet completed upon the initiation of a call on said line, a cutoif relay for said line, and a holding circuit for said magnet and cutolf relay in series through one of the talking contacts of said switch.

I. In a telephone system," a subscribers line, a switch, multiple terminals of said line at said switch, trunk lines having terminals arranged for engagement by said line terminals, a magnet for causing such engagement, a selector switch at which each trunk line terminates, a release magnet for each selector switch, and a holding circuit for said operating magnet extending through talking contacts of said switch and a contact of the release magnet of the associated selector switch.

5. In a telephone exchange system, a subscribers line, a switch, multiple terminals of said line at said switch, trunk lines having terminals arranged for engagement with said line terminals, an operating magnet for causing such engagement, a relay associated with said trunk line, a holding circuit for said magnet extending through talking contacts of said switch and said relay, a master switch, a contact oi the selected trunk at said master switch, and means controlled by said relay for causing busy potential to be applied to said contact.

6. In a telephone exchange system, a telephone line, a switch, terminals of said line at said switch, a trunk line having terminals arranged for engagement by said line terminals, an operating magnet for causing such engagement, a selector switch at which said trunk line terminates, a release magnet for said selector switch, a relay associated with said trunk, a circuit for said operating magnet closed upon the initiation of a call on said line, a holding circuit for said magnet extending through talking contacts of said first mentioned switch, said relay and a contact of said release magnet, and a circuit for said release magnet controlled by said relay while said selector switch is in its normal position.

7. In a telephone exchange system, a telephone line, a switch, multiple terminals of said line at said switch, trunk lines having terminals arranged for engagement by said lineterniinals, an operating magnet for said switch, selector switches at which said trunk lines respectively terminate, a release mag net for each of said selector switches, a line relay, a circuit for said operating magnet controlled by said line relay, a cutoff relay, a control relay associated with said trunk, and a holding circuit for said magnet extending through said cutoff relay, talking contacts of aid first mentioned switch, said control relay and a contact of said release magnet.

8. In a telephone exchange system, a telephone line, a switch, multiple terminals of said line at said switch, trunk lines having terminals arranged for engagement by said line terminals, an operating magnet for causing such engagement, a circuit for said magnet completed upon the initiation of a call on said line, a cut-oil relay for said line, and a holding circuit for said magnet and cut-oil? relay in series, said holding circuit including a portion of a talking conductor of said telephone line.

9. In a telephone system, a subscribers line, a switch, multiple terminals of said line at said switch, trunk lines having terminals arranged for engagement with said line terminals, an operating magnet for causing such engagement, a selector switch.

at which each trunk line terminates, a release magnet tor each selector switch, and a holding circuit for said operating magnet controlled through talking contacts of said switch and a contact of the release magnet of the associated selector switch.

In witness whereof, I hereunto subscribe my name this 21st day of July, A. D. 1915. CHARLES L. GOODRUM.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

' Washington, D. C. 

